Colorimetric sensor array for sensitive detection and identification of bacteria based on the etching of triangular silver nanoparticles regulated by Cl- at various concentrations

A colorimetric sensor array is proposed for ultrasensitive detection and identification of bacteria by using Cl- at various concentrations as sensing elements and triangular silver nanoparticles (T-AgNPs) as a single sensing nanoprobe. T-AgNPs are easily etched by Cl-. However, in the presence of bacteria, the etching process will be hindered. Different bacteria have differential protective effects on T-AgNPs due to their interactions, resulting in different etching degrees of T-AgNPs by Cl-, and visual color changes. By adjusting the antagonistic action between bacteria protection on T-AgNPs and the etching by using Cl- at various concentrations, different bacteria had their own color response patterns. Combined with linear discriminant analysis (LDA) and orthogonal partial least squares-discriminant analysis (OPLS-DA), the bacteria could be identified. The method was also used for bacteria mixtures identification and showed high sensitivity (OD600 = 1.0 x 10-6) for V. parahaemolyticus detection. Finally, the sensor array was successfully utilized in the identification of bacteria in pure and mineral bottled water. The method is low-cost, simple, sensitive, visual, and has potential application in point-of-care testing of bacteria.